Form2 IS Electricity (with a circuit picture)

This is a parallel circuit.
_______|l|l_________
◎-A1...................... ◎-A4
|___◎-A3__∩__∩__|
|_____◎-A2____∩__|

Key:
∩=Light bulb
◎=Ammeter
| or ______ = wires
.................=Just ignore it不用理會
問題:
Assume all the light bulbs are identical and the reading of ammeter A3 is 0.75A and A4 is 2.25A. Find the missing ammeter readings of A1 and A2. Show your steps of calculation.
A1= ___?___A
A2= ___?___A
(請用中文explain why)