Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities.
Market information
Our common stock is currently available for trading in the over-the-counter market and is quoted on the OTCQB under the symbol “PTIX.” There has been very limited market for our common stock and trading volume has been negligible. There is no guarantee that an active trading market will develop in our common stock
Trades in our common stock may be subject to Rule 15g-9 of the Exchange Act, which imposes requirements on broker/dealers who sell securities subject to the rule
to persons other than established customers and accredited investors. For transactions covered by the rule, broker/dealers must make a special suitability determination for
purchasers of the securities and receive the purchaser’s written agreement to the transaction before the sale.
The SEC also has rules that regulate broker/dealer practices in connection with transactions in “penny stocks.” Penny stocks generally are equity securities with a
price of less than $5.00 (other than securities listed on certain national exchanges, provided that the current price and volume information with respect to transactions in that
security is provided by the applicable exchange or system). The penny stock rules require a broker/dealer, before effecting a transaction in a penny stock not otherwise exempt
from the rules, to deliver a standardized risk disclosure document prepared by the SEC that provides information about penny stocks and the nature and level of risks in the
penny stock market. The broker/dealer also must provide the customer with current bid and offer quotations for the penny stock, the compensation of the broker/dealer and its
salesperson in the transaction, and monthly account statements showing the market value of each penny stock held in the customer’s account. The bid and offer quotations,
and the broker/dealer and salesperson compensation information, must be given to the customer orally or in writing before effecting the transaction, and must be given to the customer in writing before or with the customer’s confirmation. These disclosure requirements may have the effect of reducing the level of trading activity in the secondary market for shares of our common stock. As a result of these rules, investors may find it difficult to sell their shares.
Our common stock was quoted on the OTC Pink under the symbol “ATRN” prior to July 27, 2016 and then under the symbol “PTIX” between July 27, 2016 and
October 16, 2016. Commencing on October 17, 2016, our common stock is quoted in the OTCQB under the symbol “PTIX”. The following table sets forth, for the periods
indicated and as reported on the OTC Markets, the high and low bid prices for our common stock. Such quotations reflect inter-dealer prices, without retail mark-up, markdown
or commission and may not necessarily represent actual transactions.
(1) The high and low bid prices for this quarter were reported by the OTCQB marketplace. There was negligible trading volume during this period.
Table:
 | High | Low
2018(1) |  | 
First Quarter (1) | $2.20 | $1.76
Second Quarter (1) | $1.76 | $1.76
Third Quarter (1) | $2.50 | $1.25
Fourth Quarter (1) | $2.00 | $1.99
2019(1) |  | 
First Quarter (1) | $2.30 | $2.00
Second Quarter (1) | $2.00 | $1.50
Third Quarter (1) | $1.50 | $1.40
Fourth Quarter (1) | $3.80 | $1.40


Question: What is the difference between the highest and lowest bid price in 2018?
Answer: 1.25
Calculation: 2.50 - 1.25