CT1 Question bank 2.21

Can some one help me with the present value of income:-

while summing up as geometric series why have they taken N=26
when no. of years should be 25.

Thanks

 

If any one could help me with the above question

 

Yes the no. Of years is 25 but they have taken 26 because the formula for sum of gp states - Sn= (1-r*n)/(1-r)
Where n is equal to 26 as we are looking at the no. Of terms in the equation.( The equation starts with 1+v+v*2.......+v*25)

 

thanks