Data Visualization: Add points to line graph

Screen Link:

https://app.dataquest.io/m/529/guided-project%3A-storytelling-data-visualization-on-exchange-rates/6/coding-the-graph

My Code:

import numpy as np

plt.figure(figsize=(15, 6))
ax = plt.subplot()
plt.plot(euro_to_dollar['Time'],
         euro_to_dollar['US_dollar'].rolling(30).mean(), color='#154C8A',
        )
plt.xlim([np.datetime64('1999-01-04'), np.datetime64('2004-07-04')])

ax.spines['top'].set_visible(False)
ax.spines['right'].set_visible(False)
ax.spines['bottom'].set_color('gray')
ax.spines['left'].set_color('gray')

plt.ylabel('Prices', size=15,color='gray', y=0.935)
ax.tick_params(which='major', color='gray')
plt.xticks(color='gray')
plt.yticks(color='gray')

**plt.plot(x = np.datetime64('1999-04-08'), y =  euro_to_dollar['US_dollar'], **
**marker='o', markersize=3, color="red")**

plt.show()

What I expected to happen:

I would like to add points to the graph. The ‘x’ value would be the date and the ‘y’ value would be the corresponding USD amount.

plt.plot(x= Specific Date, y = Corresponding USD Value, marker=‘o’, markersize=3, color=“red”)

What actually happened:

Replace this line with the output/error