Please help in OCaml code!

2. Desugaring let and the substitution model [4] (30 minutes) Using the substitution model (including desugaring let to fun), evaluate the following expression. You may skip obvious steps (for instance, you can reduce 2+2 to 4 in a single step). Hint: Desugar all the lets to funs before doing anything else. Our evaluation took about 35 lines. Watch out for lambda shielding! let x=210 and y=3+4 in let y=14 in let z=22 in xyz