CSIR UGC NET Physical Science June 2019 Voltage Power problem

The question goes like this:

An ac signal of the type as shown in the figure, is applied across a resistor R = 1W. The power dissipated across the resistor is

Solution is below

The Slide PDF can be found here :

Csr ugc net phy june19 physics q(18 of 55) solution from bkacademy