How to print the object value in spacebar meteor

I’m struggling to print the value from an object in meteor spacebar. My object is like below -
let a = {‘1000’: 3, ‘4’: 89, ‘5’: 9898};
Also, I’ve one array i.e let b = [1000, 2000] (These values are generated dynamically but for example, I’m using the hard-coded values)

Now, I’m doing following in meteor side.

Spacebars.toHTML({a, b}, Assets.getText(‘private path of my file’));

My HTML file -

{{#each b}}
Index - {{this.[0]}}
// Now i want to fetch the ‘a’ object value basis on the b index value. as you can see here is
// that ‘1000’. how can we fetch the value from variable a like a[b] ? So that 3 would be printed
// here

Can you please help me to resolve this issue?