I wrote a program that converts celsius into fahrenheit, kelvin, and rankine. The program gives the right ouput for all other inputs, however if I input $-273\mathrm{.}15$ degrees celsius, it outputs the right answer for all the conversions except rankine. I can't figure out whats wrong. I've shown the function I use for rankine. It's a user defined function. Keep in mind that for all other inputs the formula for rankine provides the right output except for absolute $0.$