Explanation:

- The first 19 students each spent Rs 175.

- Total spent by 19 students = 19 x 175 = Rs 3,325.

- Let the average spending of all 20 students be Rs A.

- The 20th student spends Rs (A + 19).

- Total spending of 20 students = 19 x 175 + A + 19.

- The key is finding out A, the average:

1. Total spending = 20A.

2. Set up the equation: $3,325+(A+19)=20A$.

3. Simplify to find A:

- $3,344=20A-A$

- $3,344=19A$

- $A=176$

- 20th student spent = Rs 176 + 19 = Rs 195.

- Total expense = Rs 3,325 + Rs 195 = Rs 3,520.

- ?? The correct answer is Option 3: Rs 3,520.