The 21st term of an A.P. whose first two terms are -3 and 4 is

1. 17

2. 137

3. 143

4. -143

If the first term of an A.P. is -5 and the common difference is 2, then the sum of its first 6 terms is

1. 0

2. 5

3. 6

4. 15

In an A.P. if a = 1, a_n = 20 and S_n = 399, then n is

1. 19

2. 21

3. 38

4. 42

In an A.P., if a = -5, l = 21 and S = 200, then n is equal to

1. 50

2. 40

3. 32

4. 25