A rubber ball is moving in a circle while attached by a string to the ceiling. The string is $1\mathrm{.}5$ m long and makes an angle of $40$ measured from the vertical. The mass of the plane is $150$g a$-$ Find the tension in the string $(1\mathrm{.}9$N$)$ b$-$ Find the speed of the plane $(2\mathrm{.}8$m$/$s$)$