Changes in phase from solid to liquid (melting) and from liquid to gas (boiling) require energy. When solid ice melts and becomes a liquid, the particles of the substance move farther apart and heat energy is gained. When water boils, if forms steam (a gas).
<u>Answer:</u> The temperature of the system will be 1622 K
<u>Explanation:</u>
The equation relating the pre-exponential factor and activation energy follows:

where,
D = diffusion coefficient = 
= pre-exponential constant = 
= activation energy of iron in cobalt = 273,300 J/mol
R = Gas constant = 8.314 J/mol.K
T = temperature = ?
Putting values in above equation, we get:

Hence, the temperature of the system will be 1622 K
Compressibility refers to the amount or extent to which a substance can be compressed, also involving the the relationship between changes in volume due to applied pressure.
The level in the beaker will increase because the volumes of the spheres will also be added to the volume of the water. First, we must determine the volume of each sphere. For this, we will use:
density = mass / volume
We can check the density of both aluminum and iron in literature, and given the mass, we may obtain the volume.
Aluminum:
Density = 2.70 g/ml
Mass = 20.4 g
Volume = 20.4 / 2.7 = 7.56 ml
Iron:
Density = 7.87 g/ml
Mass = 49.4 g
Volume = 49.4 / 7.87 = 6.28 ml
Now, we add these volumes to the volume of water present:
75.2 + 6.28 + 7.56 = 89.04
The new level will be 89.0 ml