Evaluate the similarity between them and classify them into classes from 0-5 as follows:
0 : The two sentences are completely dissimilar.
1 : The two sentences are not equivalent, but are on the same topic.
2 : The two sentences are not equivalent, but share some details.
3 : The two sentences are roughly equivalent, but some important information differs/missing.
4 : The two sentences are mostly equivalent, but some unimportant details differ.
5 : The two sentences are completely equivalent, as they mean the same thing.

Sentence 1: A horse rider is riding a white horse. Sentence 2: A woman leading a white horse.
3

Sentence 1: Yahoo agrees to buy Tumblr for $1.1 billion cash Sentence 2: Yahoo to Buy Tumblr for $1.1 Billion
5

Sentence 1: A cat is playing a key board. Sentence 2: A man is playing two keyboards.

2