The aspirin substitute acetaminophen (C8H9O2N) is produce by the following three-step synthesis:

1) C6H5O3N(s) + 3H2 (g) + HCI(aq) >>> C6H8ONCI(s) + 2H2O(l)

2) C6H8ONCI(s) + NaOH(aq)>>> C6H7ON(s)+ H2O(l) + NaCl(S)

3) C6H7ON(s) + C4H6O3(l)>>> C8H9O2N(s) + HC2H3O2(l)

The first two reactions have percent yields of 87% and 98% by mass, respectively. The overall reaction yields 3 mol of acetaminophen product, C8H9O2N, for every 4 mol of C6H5O3N reacted.

a) what is the percent yield by mass for the overall process?

b)what is the percent yield by mass of step 3?

how do i go about doing this? i dont even know where to start? she might try and trick us to with unbalanced equations.

PLEASE HELP ME!!!!