A 1lb box costs .50 to mail through the postal service. a 3lb box cost .92 to mail through the postal service. the postal services calculates the weight to the whole pound. what functions represent the total cost f(x), to send a letter that is x pounds? select all that apply.
A- f(x)=0.21(x-1)+0.50
B- f(x)=0.50(x-1)+0.21
C- f(x)=0.50x
D- f(x)=0.21x+0.29
E- f(x)=0.21x