Write a code to do the following tasks in given order
1) clean the screen
2) delete all variables in workspace
3) Define symbolic variable x
4) Define symbolic function f as f(x)=x²+4x−15
5) Take first derivative of function f and assign it to function g
6) Take first derivative of function g and assign it to function h
7) Take second derivative of function f
8) Define symbolic variables s and t
9) Define symbolic function k as k(s,t)=cos(s²/t)
10) Calculate the partial derivative ∂k/∂t and assign to function I
11) Calculate the partial derivative ∂k/∂s and assign to function m
12) Calculate the partial derivative ∂m/∂t and assign to function n
13) Calculate the partial derivative ∂l/∂s and assign to function o