Describe qualitatively how the tm for a double-stranded dna depends on its nucleotide composition

I think the higher the proportion of Guanine and cytosine; then the higher the melting temperature,tm. This is because there are three hydrogen bonds between the bases pairing between G and C, thus more thermal energy will be required to break the three hydrogen bonds holding G and C pairs, as compared to the breaking the two hydrogen bonds bonds holding A=T pairs. 

1.989×10^30 kg is the weight of the sun.