Which of the following sentences are propositions? What are the truth values of those that are propositions?

a$.$ Ipoh is the capital of Perak.

b$.2+3=7.$

c$.$ Open the door.

d

e$.$ The moon is a satelite of the earth.

f$.x+5=7.$

g$.x+5>9$ for every real number $x.$

What is the negation of each of the following propositions?

a$.$ Kuala Kangsar is the capital of Perak.

b$.$ Food is not expensive in the UTHM.

c$.3+5=7.$

d$.$ The summer in Johor is hot and sunny.