we know that
zeros of any function f(x) are values of x where f(x)=0
Here , f(x) is profit function
so, f(x)=0 when x=15 and x=70
f(x)=0 means profit is 0
and profit is zero means neither gain nor loss
so, woodworker won't either loss or gain when x=15 and x=70
so, option-B.........Answer