The self inductance L of a solenoid of length $l$ and area of cross section A, with a fixed number of turns N increases as

Question

$(a) l\; and A \; increases$
$(b) l\; decreases \; and \; A\;increases$
$(c) l\; increases \; and \; A\;decreases$
$(d) l \; and\; A \; decreases$