$3.$ Symbolize the following propositions, which can be of any form, using the provided dictionary

p $=$ Prague t $=$ Tokyo l $=$ London r $=$ Rio de Janeiro

Bx $$ x is big. Cx $$ x is a city.

Ex $$ x is expensive. Tx $$ x has tourist attractions.

Sx $$ x should be visited.

a$.$ Some big cities are expensive, but Prague isn$$t$.$