Sampling MCQ

20% of payable balance is being tested . Testing resuts show that there is a $45000 error in sample , $20000 which is due to invoices not being recorded in the correct period as a result of weak controls and additionally there is a one off error of $25000 which was made by clerk

What would be an appropriate course on basis of these results?
a)Error is immaterial and therefore no further work is required
b)Effect of control error should be projected across whole population
c)Company should be asked to adjust parables fig by $45000
d)Different sample should be selected as these results are not reflective of population

Sir correct ans is B , please can you explain