If $N = \frac{\sqrt{7} - \sqrt{3}}{\sqrt{7} + \sqrt{3}}$,then what is the value of $N + \frac{1}{N}$?

What should come in place of the question mark $(?)$ in the following expression?
$(674.87 + 59.98) \div 35.02 = ?$

$40.83 \times 1.02 \times 1.2 = ?$

If $ab + bc + ca = 0$,then the value of $\left(\frac{1}{a^2 - bc} + \frac{1}{b^2 - ca} + \frac{1}{c^2 - ab}\right)$ is

If $2p + \frac{1}{p} = 4$,then the value of $p^{3} + \frac{1}{8p^{3}}$ is:

In an examination,a student scores $4$ marks for every correct answer and loses $1$ mark for every wrong answer. If he attempts in all $60$ questions and secures $130$ marks,the number of questions he attempts correctly is