Mark the correct alternative in the following:

Let denote the sum of first n terms of an A.P. If , then is equal to

Mark the correct alternative in the following:

If in an A.P., and , where denotes the sum of r terms of the A.P., then is equal to

Mark the correct alternative in the following:

If in an A.P., the pth term is q and term is zero, then the term is

Mark the correct alternative in the following:

The 10^th common term between the A.P.s 3, 7, 11, 15, ... and 1, 6, 11, 16, ... is

Mark the correct alternative in the following:

If in an A.P. and , where denotes the sum r terms of the A.P., then equals