To calculate the elasticity of supply using the point method, we need to use the formula:

Elasticity of Supply = (% Change in Quantity Supplied) / (% Change in Price)

Given that the supply function is Q = 100 + 10p, where Q represents quantity supplied and p represents price, we can calculate the elasticity using the point method.

Step 1: Determine the initial price and quantity supplied
Let's assume the initial price is p1 = 10. Substituting this value into the supply function, we can find the initial quantity supplied:
Q1 = 100 + 10(10) = 100 + 100 = 200

Step 2: Determine the new price and quantity supplied
Let's assume the new price is p2 = 15. Substituting this value into the supply function, we can find the new quantity supplied:
Q2 = 100 + 10(15) = 100 + 150 = 250

Step 3: Calculate the percentage change in quantity supplied
The percentage change in quantity supplied is given by the formula:
% Change in Quantity Supplied = (Q2 - Q1) / Q1 * 100

Substituting the values, we get:
% Change in Quantity Supplied = (250 - 200) / 200 * 100 = 50 / 200 * 100 = 25%

Step 4: Calculate the percentage change in price
The percentage change in price is given by the formula:
% Change in Price = (p2 - p1) / p1 * 100

Substituting the values, we get:
% Change in Price = (15 - 10) / 10 * 100 = 5 / 10 * 100 = 50%

Step 5: Calculate the elasticity of supply
Finally, we can calculate the elasticity of supply using the formula:
Elasticity of Supply = (% Change in Quantity Supplied) / (% Change in Price)

Substituting the values, we get:
Elasticity of Supply = 25% / 50% = 0.5

Since the elasticity of supply is a positive value less than 1, we can conclude that the supply is inelastic.

Therefore, the correct option is d) 3.