A Saudi Arabian black oil has a bubble$-$point pressure of $1250$ psia at reservoir temperature of $142F.$ Producing gas$-$oil ratio $(R_p)$ is $364$ SCF$/$STB of $0\mathrm{.}872$ specific gravity gas and $40\mathrm{.}2$ API stock$-$tank oil. Estimate the oil viscosity at the initial reservoir pressure of $2880a.$