Consider the following chart. After which worker does the marginal product of labor $($MPL$)$ begin to decrease?Land$(10$ Acres$)(1)$Labor $($Workers$)(2)$Total Product$($Pounds$)(3)$Marginal Product of Labor $($MPL$)(4)10$ acres$00-10$ acres$15010$ acres$212010$ acres$320010$ acres$430010$ acres$538010$ acres$640010$ acres$7390$a$.)$After the fourth workerb.$)$After the third workerc.$)$After the fifth workerd.$)$After the $2$nd worker