Answer:
Payback period (A)  is 3.44 years
Payback period (B)  is  2.39 years
Explanation:
Cash Flow (A)   –$428,000; $42,500;  $63,500;  $80,500;  $543,000
Cash Flow (B)   –$41,500; $20,700; $13,000; $20,100; $16,900
The payback period will note consider discounting rate, thus we do manual counting till the cash flow equal to zero (0) 
Payback period = Number of Years immediately preceding year of break-even + (investment - cashflow of Years immediately preceding year of break-even)/ cashflow of year break- even
Project A will be break even in Year 4, then 
Payback period (A)  = 3 years + ($428,000 - ($42,500+$63,500+$80,500))/ $543,000 = 3.44 years
Project B will be break even in Year 3, then 
Payback period (B)  = 2 years + ($41,500 - ($20,700+$13,000))/$20,100 = 3.44 years = 2.39 years