A certain amount of ice is supplied heat at a constant rate for 7 min. For the first one minute the temperature rises uniformly with time. Then it remains constant for the next 4 min and again the temperature rises at uniform rate for the last 2 min. Given `S_("ice")=0.5cal//g^(@)C,L_(f)=80cal//g`.
The initial temperature of ice is
A. `-10^(@)C`
B. `-20^(@)C`
C. `-30^(@)C`
D. `-40^(@)C`
