The value of can be computed according to the following formula:

a$.$ pi$=1-1/3+1/5-1/7+1/9-...$

b$.$ Write an algorithm to compute $.$ Because the formula is an infinite series and an algorithm must stop after a infinite number of steps, you should stop when you have the result determined to six significant digits $($pi$=3\mathrm{.}14159).$