Question 862065
For therms up to 60, the function based on the listing of charges is 
{{{C=10.25+0.24228x+0.267x}}}
{{{highlight(C=10.25+0.50928x)}}}
The information about "Gas charge" does not indicate if it is for more or less than 60 therms, so my best interpretation is to include it in both function branches.


For more than 60 therms, the function must be,
{{{C=10.250.23559x+0.267x}}}
{{{highlight(C=10.25+0.74487x)}}}


None of the information in the description gives any justification for  a term of 10.63 in the second branch of the function.


FURTHER THOUGHT:  For OVER 60 therms, you would have 60 therms plus x-60 therms.
 This may mean charge of {{{60*0.24228+(x-60)*(0.23599)}}}
{{{14.5368+0.23599x-60(0.23599)}}}
{{{14.5368+0.23599x-14.1594}}}
{{{0.3774+0.23599x}}}
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Note that {{{highlight(10.25+0.3774=10.6274)}}}, which is to the nearest hundredths place, {{{highlight(10.63)}}}.