To the eye – taken by itself – Alpha Centauri A appears as the fourth-brightest star seen from Earth, just slightly outshone by Arcturus. However, the combined light of Alpha Centauri A and B is slightly greater than Arcturus, so in that sense it appears as the third-brightest star visible in Earth's sky.
Light is one form of energy that travels in electromagnetic waves. This energy is both magnetic and electrical. There are many different types of electromagnetic (EM) waves.
Given is the specific heat of water equal to 4.18 Joule per gram per *C.
This means to raise the temperature of 1 g of water by 1 degree Celsius we need 4.18 joule of energy.
Now, look at the question. We are asked that how much amount of energy would be required to raise the temperature of 25 g of water by (54-50) = 4 degree celsius.
To do so we have formula
Q = m C (temperature difference)
Have a look at pic for answer