Hello,
We have both of iOS and Android teams of developers as well as own designer. They have experience in developing calculator apps. Please check the attached sample.
InMotionSoft provides 6 months warranty period on our coding. It means if any bug appears after release it would be fixed at no cost for you.
Also we can upload your app as to AppStore so to GooglePlay. This service is also included into our post release support policy.
I would like to discuss your project in details to provide you our clear time and price estimation.
Looking forward
Ivan Fortuna
Business Developer Manager at InMotionSoft