Let R be a region in the first quadrant of the xy plane enclosed by a closed curve C considered in counter-clockwise direction. Which of the following expressions does not represent the area of the region R?

Let $$\overrightarrow E (x,y,z) = 2{x^2}\widehat i + 5y\widehat j + 3z\widehat k$$. The value of $$\mathop{\int\!\!\!\int\!\!\!\int}\limits_{\kern-5.5pt V} {(\overrightarrow \nabla \,.\,\overrightarrow E )dV} $$, where V is the volume enclosed by the unit cube defined by 0 $$\le$$ x $$\le$$ 1, 0 $$\le$$ y $$\le$$ 1, and 0 $$\le$$ z $$\le$$ 1, is

Let the probability density function of a random variable x be given as

f(x) = ae^$$-$$2|x|

The value of a is _________.

A charger supplies 100 W at 20 V for charging the battery of a laptop. The power devices, used in the converter inside the charger, operate at a switching frequency of 200 kHz. Which power device is best suited for this purpose?