Answer:
To work out the charges for the job, we first need to calculate how many hours Pierre worked on the job.
She started at 9:30 am and finished at 1:00 pm, which means she worked for:
1:00 pm - 9:30 am = 3.5 hours
Now, we can use the formula C=20+30t, where t is the number of hours worked (in this case, 3.5) to calculate the charges for the job:
C = 20 + 30(3.5)
C = 20 + 105
C = 125
Therefore, Pierre should charge $125 for the job.