Hehehe. Saya minta tolong lagi boleh....

Q = m . c . ΔT

7) 3900 = m . 3,9 x 10^3 . 1
m = 3900 ÷ 3,9 x 10^3
m = 1 kg ( C )

8) Q = 1 . 900 . 20
= 18.000 joule ( A )