The parallelogram structural element given in the figure below is subjected to a load and its edges QA and BC are shortened by $0\mathrm{.}003$ mm and rotated by $500$ radians counterclockwise, while its edges $AB$ and QC are lengthened by $0\mathrm{.}004$ mm and rotated by $1000$ radians clockwise. Calculate the magnitudes and directions of the principal deformations at point $Q.a=20mm$ and $b=12$ mm $.$