Heat loss from a hot water tank

[sci0x]

Homework Statement

Water in an insulated hot water tank is maintained at 80 degrees C. The external area of tank is 35m2. Calculate heat loss by i) convection ii) radiation

Relevant Equations

Q=UAdT

This is a past exam paper Q.
I think i might be missing info though.

For i) i use q=UAdT
A= 35m2
dT= (80-20)
They haven't given U but if i know answer should be 1,050W
So if i set U to 0.5

(0.5)(35)(60)
= 1050W

Am i missing something or could I calculate U with the info given?

Also ii)
Use stefan-boltzmann eq:

P = E(Stefan constant)(Area)(T^4 - T^4 in kelvin)
I don't have E the emissivity coefficient
Stefan constant is 5.67 x 10-8
80 degrees in K is 353.15
20 degrees in K is 293.15
P=E(162107.003)

The answer should be 643W
Can i calculate radiation from info given?

 

[TSny]

Your work looks ok to me, except the decimal point is off in P=E(162107.003) .

The values of U and E should have been provided in the exam.