65 Grams is the mass of the beaker because you just take the mass of Water + Beaker and take the water away now you have the mass of the beaker
Q=mc(delta T)
m= Q/ c(delta T)
m= 1200 J / (4.19 J/kg C) (15-10)
m= 57. 28 kg
The equation you use here is
mass =moles x Mr
So:
Moles of K - 0.55mol
Mr of K - 39.1
Mass= 0.55x39.1 =21.505g
Do length x width x height which is 10 cm x 8.2 cm and 3.5 cm. Pay close attention to sig figs as well (or if your teacher doesn't mind all that much then don't fret about it, but mine's really picky!)
