The area of a trapezoidal parcel of land is computed as follows:

area = [(a1 + a2)/2]*b

Where a1, a2 and b are independently measured dimensions. If measured values for a1, a2 and b are 319.414 m, 481.112m, and 502.307 m, respectively with variances 0.030 m², 0.042 m^2, and 0.020 m², respectively. Compute the area of the parcel and the standard deviation of this computed area. (Note the given are variances and what is asked is the standard deviation) Use matrix solution.