Deep mixing is a ground improvement method developed for soft soils like$$ clay, silt, and peat. Swedish civil engineers investigated the properties of soil improved by deep mixing with$$ lime$-$cement columns in the journal Giorisk$($Vol$.7,2013).$ The mixed soil was tested by advancing a cylindrical rod with a cone tip down into the soil. During$$ penetration, the cone penetrometer measures the cone tip resistance$($megapascals$,$ MPa$).$ The researchers established that tip resistance for the deep mixed soil followed a normal distribution with muequals$2\mathrm{.}2$ MPa and sigmaequals$0\mathrm{.}9$ MPa. Complete parts a through c below. Find a value of tip$$ resistance, T$,$ such that $15\%$ of all soil samples have tip resistance values that exceed T$.$