Read a wave from its equation

A wave is $y = a\sin(bx + c) + d$ with $a = -2.5$, $b = 3$, $c = 1.2$ and $d = 4$. Find its amplitude, its period, its highest and lowest values, and the first $x > 0$ where it is highest. The program then draws it, so you can see your answers.

The idea. Because $a < 0$, the wave is highest where the sine is $-1$, that is where $bx + c = \dfrac{3\pi}{2} + 2n\pi$.

Your tasks.

1. Set amplitude and period.
2. Set highest and lowest.
3. Set first_top to the smallest $x > 0$ where $y$ is highest.