$y=f\left(x\right)$ is a linear function in x. When value of x is 9, the value of f(x) is 40 and when value of x is 19, the value of f(x) is 70. Find the function f(x).

Express the area $A$ of a square as a function of its perimeter $P$.

The price of a share is given by the following equation.

$P\left(x\right)=3.7\sin \left(\frac{\pi }{113}\right(x-73\left)\right)+17$

Where x is the number of days after the share is launched.

Determine the period of P(x).

The cost function C(x) and the selling price of each article, p(x) are given below. Determine the profit function P(x).

$C\left(x\right)=-0.03x^2+70x+75$

$p\left(x\right)=80$

From the edge of a cliff 48 m above the ground, a ball is vertically thrown upward at a velocity of 16 m/s. The function $h\left(t\right)=-4t^2+16t+48$ represents its height above the ground after it is thrown, where t is time in seconds. Determine the time at which the ball hits the ground.