Kevin is an auto mechanic. He spends $3$ hours when he replaces the shocks on a car and $2$ hours when he replaces the brakes. He works no more than $42$ hours a week. He routinely completes at least $4$ shocks replacements and $6$ brake replacements a week. If he charges $$$$450$ for labor replacing shocks and $$$$200$ in labor for replacing$$ brakes, how many jobs of each type should he complete a week to maximize his$$ income?