$$ A thermocouple with linear calibration : $0$ C $400$ C$.$

$$ emf at max. temperature $($reference junction temperature $0$ C$)$ is $20\mathrm{.}68$ mV$.$

a$)$ Calculate the correction which must be made to the indicated emf if the cold junction temperature is $25$ C$.$

b$)$ If the indicated emf is $8\mathrm{.}92$ mV in the thermocouple circuit, determine the temperature of the hot junction.