Answer :
The equation for his currnet sales can be as follows:
x=520*2^n
n is the current month
We are looking for the sum of next 3 months, so n+1, n+2 and n+3.
520*2^(n+1)+520*2^(n+2)+520*2^(n+3)=520*4+520*8+520*16=2080+4160+8320=14560
x=520*2^n
n is the current month
We are looking for the sum of next 3 months, so n+1, n+2 and n+3.
520*2^(n+1)+520*2^(n+2)+520*2^(n+3)=520*4+520*8+520*16=2080+4160+8320=14560