To solve this problem it is necessary to apply the concepts related to the Power depending on the temperature and the heat transferred.
By definition the power can be expressed as

Where,
Change at the temperature, i.e, the maximum acceptable die temperature (
) with the allowable temperature in chassis (
)
Change in the thermal resistance to ambient (
) and the Thermal resistance from die to package (
)
Our values are given as,




Replacing we have,


The power that can dissipate the chip is 10W