Malonic ester (diethyl malonate) is treated successively with sodium ethoxide (1 ethyl bromide, potassium tert-butoxide, isobutyl chloride, hot aqueous naoh, hcl, and heat. what is the final product?

In first step the acidic proton at alpha position is abstracted by NaOEt and forms Enolate.
The resulting enolate undergoes SN² reaction with Ethyl Bromide.
The resulting product again on treatment with Potassium tertiary Butoxide gives corresponding Enolate.
This second enolate on treatment with Isobutyl Chloride undergo SN² reaction.
At last treatment with NaOH (aq) and HCl at high temperature yield 2-Ethyl-4-methylpentanoic Acid.