(20 pts) An electric kettle is an indispensable appliance of our daily life used to boil water quickly. Electric kettles are very well insulated and their heating coils either sit in the water or embedded at the bottom to form a flat metal surface. When water boils, the kettles stop operation automatically and the bubbles and/or vapor formed disappear shortly. For the final exam of a precious 321 class of spring 2021 , one instructor put 1L of water into a kettle (14cm diameter circular flat metal surface) at his house and recorded the time of boiling as 3.5min. a. The seller claims the power of kettle to be 2000W, on the catalogue. Is it right? b. The instructor's son, Ulus, wonders how hot the surface is at the time of boiling. Because there was no thermocouple to measure it, would you estimate the surface temperature? (Data: initial temperature of water: 20C, boiling temperature of water 100C, specific heat of water: 4200J/kg.C, and density of water 1g/mL )