Estimate each of the follwoing by rounding off each number to nearest tens:
(a) 11963 – 9369
(b) 76877 – 7783
(c) 10732 – 4354
(d) 78203 – 16407
(a) 11960 – 9370=2590
(b) 76880 – 7780=69100
(c) 10730 – 4350=6380
(d) 78200 – 16410=61790