Electrical quantities — practice question

A student carries out an investigation into the electrostatic charges on three objects, P, Q and R. The student puts object P on the insulated pan of a balance and records the balance reading. Next, the student holds object Q a short distance above object P and records the balance reading. Lastly, the student holds object R the same short distance above object P and records the balance reading. The student’s results are shown. Which row gives charges that could account for these results?