Suppose a string of digits s in base base contains up to one fractional point. Complete the function, eval_strfrac(s, base), so that it returns its corresponding floating-point value. Your function should always return a value of type float, even if the input happens to correspond to an exact integer. Examples: eval_strfrac('3.14', base=10) ~= 3.14 eval_strfrac('100.101', base=2) == 4.625 eval_strfrac('2c', base=16) ~= 44.0