Prediction of magnetic and magnetocaloric properties in $$\hbox {Pr}_{0.8-x}\hbox {Bi}_{x}\hbox {Sr}_{0.2}\hbox {MnO}_{3}$$Pr0.8-xBixSr0.2MnO3 ($$x=0$$x=0, 0.05 and 0.1) manganites