A block with an elastic modulus $E=105$GPa and a Poisson's ratio $v=0\mathrm{.}33$ produced stress $Ox=250$MPa, oy $=-75$MPa, and $0Z=0.$ The dimensions before the stress occurred were $L=120mm,a=60mm,$ and $b=20mm.$ After the stress is generated, calculate the dimensions $L,a,$ and $b$ of the block.