1-what is Ln in Q1 AND Q2 EQUATIONS??

2-What is (v2/v3) and (v4/v3) in EQUATIONS Q1 AND Q2

slope of a curve is the tangent of angle made by the slope with the positive x axis .

But in selected seconds sir took angle with negetive direction of x axis

a carnot engine whoose sink is at 300k has an efficiency of40percent by how much should the temperature of the source be increased so as to increase its its efficiency by 50percent of original efficiency?