Answer:
heterozygous with genotype "Ll" and phenotype heterozygotic tall.
Explanation:
Let us assume that the trait for long-coat be dominant over the trait of short trait.
Let the allele for long-coat trait be represented by "L" and the allele for short-coat trait be represented by "l"
The genotype of true breeding long-coat dog will be "LL"
and the genotype of true breeding short-coat dog will be "ll"
When these two species are crossed with each other, following offspring are produced
LL * ll
Ll, Ll, Ll, Ll
this means that all the offspring will be heterozygous with genotype "Ll" and phenotype heterozygotic tall.