An unloaded pontoon $($floating structure$)$ being used in a port to transport construction

equipment has a mass of $15$ tonnes. In plan the pontoon is $8$ m long by $5$ m wide. It is

rectangular in section and has sides $1\mathrm{.}5$ m high. The water is saline with density of $1025$ kg$/$m$^3.$

a$)$ What is the depth of immersion of the unloaded pontoon? $(4$ marks$)$

b$)$ What weight can be carried by the pontoon while still maintaining a freeboard of $0\mathrm{.}5$

m$?(6$ marks$)$