As a part of producing mosfet transistors, a p-type silicon (si) wafer containing boron (b) dopants at a concentration of 1x10^19 atoms/cm^3 is being processed to create a pn junction by doping the wafer with phosphorous (p) atoms using a p-producing gas. assume that the wafer does not contain p prior to the diffusion process. the solubility of p in si at 1000°c is 1x10^20 atoms/cm^3. it is determined that the pn junction depth of 1 um was produced after 60 minutes at 1000°c. the activation energy for estimating the diffusion coefficient of p in si is 2.5x10^5 j/mole. based on this result, estimate the pre-exponential constant for the diffusion coefficient of p in si at 1000°c in cm^2/s.