**Mr. A's Salary Breakdown**

**Basic Salary - 4000:**
The basic salary is the fixed amount paid to an employee before any additional allowances or deductions are applied. In this case, Mr. A's basic salary is 4000.

**Dearness Allowance - 15000:**
Dearness allowance (DA) is an allowance provided to employees to help them cope with the rising cost of living. It is usually a percentage of the basic salary. In this case, Mr. A receives a dearness allowance of 15000.

**Entertaining Allowance - 1000:**
Entertaining allowance is given to employees to cover the expenses they may incur while entertaining clients or business associates. In this case, Mr. A receives an entertaining allowance of 1000.

**Medical Allowance - 5000:**
Medical allowance is provided to employees to cover their medical expenses. It is usually a fixed amount or a percentage of the basic salary. In this case, Mr. A receives a medical allowance of 5000.

**House Rent Allowance - 12000:**
House rent allowance (HRA) is provided to employees to help them meet the cost of renting a house. It is usually a percentage of the basic salary. In this case, Mr. A receives a house rent allowance of 12000.

**Rent Paid for House - 15000:**
Rent paid for a house is the actual amount Mr. A pays as rent for his accommodation. In this case, Mr. A pays a rent of 15000 for his house.

**Calculation of Net Salary:**

To calculate Mr. A's net salary, we need to subtract the rent paid for the house from the house rent allowance and add it to the basic salary and other allowances.

Net Salary = Basic Salary + Dearness Allowance + Entertaining Allowance + Medical Allowance + (House Rent Allowance - Rent Paid for House)

Net Salary = 4000 + 15000 + 1000 + 5000 + (12000 - 15000)

Net Salary = 4000 + 15000 + 1000 + 5000 - 3000

Net Salary = 24000

Therefore, Mr. A's net salary is 24000 after considering all the allowances and deductions.