objective functions and constraints statements

Hi,

I am trying to answer the following question:

Grow It Co is trying to formulate its optimal production plan. It grows two products tomatoes and beans. Each batch of plants can be sold for $30 and $18 respectively.
Variable costs per unit of the two products are as follows:

Tomatoes Beans
$ $
Fertiliser (@ $1 per 100g) 2 5
Labour (@$8 per hour) 16 8
Other variable costs 1 1
Total 19 14

Next month, only, 100 kg of material and 5,000 labour hours are available. The company aims to maximise its profits each month.

The company wants to use a linear programming model to establish an optimal production plan. The model considers “t” to be number of batches of tomatoes to grow and “b” the number of batches of beans.
Which of the following objective functions and constraints statements (relating to material and labour respectively) is correct?
Choose one:

Objective function Material constraint Labour constraint
A 30t+18b 0.2t+0.5b 2t+b?5000
B 11t+4b 0.2t+0.5b?100 2t+b?5000
C 11t+4b 2t+5b?100 16t+8b?5000
D 30t+18b 2t+5b?100 16t+8b?5000

(Hope the formatting is OK)

I think the answer is b… only because initially I got 11t + 4b as the objective function, 2t+b?100 and 2t+b?5000 which isn’t an answer above.
Then I realised the fertiliser is priced in grams not Kilograms…
But I’m totally lost as to how I prove material constraint is 0.2t+0.5?100.

Or am totally wrong?!