Some mammoth bones found in Arizona were found by carbon-14 dating to be 1.13 104 years

Question:

Some mammoth bones found in Arizona were found by carbon-14 dating to be 1.13 × 104 years old. What must have been the activity of the carbon-14 in the bones in disintegrations per minute per gram? Assume the original activity was 15.3 disintegrations per minute per gram.