Al's Shoeshine Stand shined 1,000 pairs of shoes last year and 1,200 pairs this year. He charged

Question:

Al's Shoeshine Stand shined 1,000 pairs of shoes last year and 1,200 pairs this year. He charged $4 for a shine last year and $5 this year. If last year is taken as the base year, find Al's contribution to both nominal GDP and real GDP in both years.
Which measure would be better to use if you were trying to measure the change in Al's productivity over the past year? Why?