$13-8.$ A housekeeper hangs a wet blanket out to dry in a high wind. The blanket weighs $4$ lb dry and $16$ lb wet and has dimensions of $7$ ft by $8$ ft $.$ Assume outdoor conditions of $90$ Fdb and $50$ percent relative humidity and that the blanket is at a temperature of $90$ F $.$ Estimate the time required for the blanket to become dry if the average heat$-$transfer coefficient on the exposed side of the blanket is $4Bt\frac{u}{hr-f{t}^2-F}.$