Minor Typos in Notebook 002

[Haniiko1]

• In section 8, 2nd code block, the variable name for substrate concentrations should be substrate_concs instead of subtrate_concs. The code would still work if all of the code blocks above this one are ran before hand.
• In Exercise section, there is a small typo, which is nmbers instead of numbers.
• Small typo in Wrap Up Text. Congratulations on completing notebook 004 instead of notebook 002.