How many integers between 6000 and 7000 that have distinct digits and increase from left to right ?  Choose the correct answer:
A) 10	B) 20	C) 60	D) 80	E) 600
Since the numbers must be distinct and increasing from left to right,   The only arrangements we could come-up with are:   645_ --&gt; 4   646_ --&gt; 3   647_ --&gt; 2   648_ --&gt; 1   656_ --&gt; 3   657_ --&gt; 2   658_ --&gt; 1   667_ --&gt; 2   668_ --&gt; 1   678_ --&gt; 1   Number of integers =20   20
<result>B</result>
How many integers between 6000 and 7000 that have distinct digits and increase from left to right ?