Given data:
- Total staff: 2000
- Percentage of staff who prefer coffee: 48%
- Percentage of staff who prefer tea: 54%
- Percentage of staff who prefer cocoa: 64%
- Percentage of staff who use coffee and tea: 28%
- Percentage of staff who use tea and cocoa: 32%
- Percentage of staff who use coffee and cocoa: 30%
- Percentage of staff who use none of these: 6%

Let's solve the problem step by step:

Step 1: Calculating the number of staff who prefer each beverage.
- Number of staff who prefer coffee = 48% of 2000 = 0.48 * 2000 = 960
- Number of staff who prefer tea = 54% of 2000 = 0.54 * 2000 = 1080
- Number of staff who prefer cocoa = 64% of 2000 = 0.64 * 2000 = 1280

Step 2: Calculating the number of staff who use multiple beverages.
- Number of staff who use coffee and tea = 28% of 2000 = 0.28 * 2000 = 560
- Number of staff who use tea and cocoa = 32% of 2000 = 0.32 * 2000 = 640
- Number of staff who use coffee and cocoa = 30% of 2000 = 0.30 * 2000 = 600

Step 3: Calculating the number of staff who use none of these.
- Number of staff who use none of these = 6% of 2000 = 0.06 * 2000 = 120

Step 4: Calculating the number of staff who use tea and cocoa but not coffee.
- Number of staff who use coffee, tea, and cocoa = Number of staff who use coffee and tea + Number of staff who use tea and cocoa + Number of staff who use coffee and cocoa - 2 * Number of staff who use all three beverages
- Number of staff who use coffee, tea, and cocoa = 560 + 640 + 600 - 2 * Number of staff who use all three beverages

Step 5: Calculating the number of staff who use all three beverages.
- Number of staff who use all three beverages = Percentage of staff who use coffee, tea, and cocoa / 100 * Total staff
- Number of staff who use all three beverages = 28% of 2000 = 0.28 * 2000 = 560

Step 6: Calculating the number of staff who use tea and cocoa but not coffee.
- Number of staff who use tea and cocoa but not coffee = Number of staff who use coffee, tea, and cocoa - Number of staff who use all three beverages
- Number of staff who use tea and cocoa but not coffee = 560 - 560 = 0

Therefore, the number of staff who use tea and cocoa but not coffee is 0.

The correct answer is (d) none.

Answer is 280 not 0