A student studies for X number of hours during a randomly selected school day. The probability that X can take the values, has the following form, where k is some constant.

$$ \mathrm{P}(\mathrm{X}=x)= \begin{cases}0.2, & \text { if } x=0 \\ \mathrm{k} x, & \text { if } x=1 \text { or } 2 \\ \mathrm{k}(6-x), & \text { if } x=3 \text { or } 4 \\ 0, & \text { otherwise }\end{cases} $$

The probability that the student studies for at most two hours is

In an LC circuit, angular frequency at resonance is $\omega$. The new angular frequency when inductance is made four times and capacitance is made eight times is

$$ \text { The electric flux through the surface } $$

A person observes two moving trains. First reaching the station and another leaves the station with equal speed of $30 \mathrm{~m} / \mathrm{s}$. If both trains emit sounds of frequency 300 Hz , difference of frequencies heard by the person will be (speed of sound in air $330 \mathrm{~m} / \mathrm{s}$ )